Speckle Image Processing Research Articles

Improving surface plasmon resonance sensors with speckle image processing

This paper investigates digital image correlation approaches for assessing speckle patterns produced by surface plasmon resonance (SPR) imaging. An SPR sensor based on the Kretschmann setup comprising a gold-coated prism in a fixed angular position performs refractive index assessments in ethanol solutions. Subsequently, the acquisition system collects the reflected light and processes the speckle field images to evaluate the sensor's sensitivity, noise, and limit of detection. Based on three repetitions under similar conditions, the maximum resolution for the average intensity, zero-mean normalized cross-correlation, and the relative sum of square differences metrics are 4.90×10−4, 2.31×10−5, and 7.45×10−6 RIU, respectively, leading to an improved limit of detection without modifying the optical setup.

A lightweight real-time smartphone-based laser speckle contrast analyzer

Recently, laser speckle contrast analysis (LASCA) technology has spurred the exploration to instantly visualize microcirculatory tissue blood perfusion in clinical diagnosis, due to its non-contact, non-invasive and rapid imaging advantages. However, traditional medical imaging systems used to perform laser speckle contrast imaging (LSCI) are expensive and their transportation needs prudence, limiting the wide availability of LASCA for personal preliminary diagnosis. In this article, a low-cost, lightweight and portable smartphone-based laser speckle contrast imaging (smartphone-LSCI) is proposed to address this issue. With a built-in image sensor and powerful computational capability of the smartphone, the proposed system could be utilized to estimate the speckle contrast of human skin under various conditions and obtain information of the blood flow velocity of capillaries along with the degree of blood perfusion. Through experiments and theoretical analysis, we systematically studied the feasibility and robustness of image sensors on smartphones-LSCI. Experiments prove that ambient light has little influence on the performance of our smartphone-LSCI. In addition, the speckle image processing flow of smartphone-LSCI is proposed, together with an enhanced spatial LASCA (esLASCA) method. In the experiments with a low-cost smartphone, i.e., Redmi K40, the 4000×3000 pixels images can be processed at a frame rate of 20Hz. The consumption time of both the existing state-of-the-art roll algorithm and the proposed esLASCA is linearly proportional to the width (height) of the image resolution. However, our proposed method shows a slower growth rate and lower computational time when the window size is small.

Terbium doped zinc ortho titanate nanocomposite for optical application – A complementary theoretical calculations

Zinc ortho titanate nanomaterial was synthesized hydrothermally under surfactant free conditions. The crystalline nature of the synthesized nano composite has been affirmed by PXRD analysis. FTIR analysis reports the existence of Ti-O and Zn-O metal organic bonds at 495 and 558 cm-1 respectively. UV cut off wavelength was found to be 232 nm which is evident that the narrow transparent window was in the entire visible region. The structural morphology and elemental analyses have been confirmed by SEM and EDX respectively and as well characterized by photoluminescence, scanning electron microscopy and thermal analysis. The SEM image is further analyzed and compared with laser speckle image processing. Thermal analysis evidenced the stability of the nano composite up to 990 °C which suitable to thermal devices. To reinforce the experimental findings, theoretical calculations were carried out using DFT functional B3LYP/cc-pvtz level of basis set through Gaussian 09 program.

Synthesis of the optimal algorithm and structure of contactless optical device for estimating the parameters of statistically uneven surfaces

The production of parts and (or) finished products in electronics, mechanical engineering and other industries is inextricably linked with the control of the accuracy and cleanliness of the processed surfaces. Currently existing meters of parameters of statistically uneven surfaces, both contact and non-contact have some disadvantages, as well as limitations due to methods and design features of measurement. Speckle interferometric methods for measuring parameters of statistically uneven surfaces make it possible to get away from some disadvantages inherent in existing methods and measurements. The use of methods of statistical radio engineering, methods of optimization of statistical solutions and estimates of parameters of predictive distributions for optimal radio engineering system synthesis is promising for the analysis and processing optical-electronic coherent laser space-time signals (speckle images) form with the laser radiation scattered by statistically uneven surfaces. This work synthesizes the optimal algorithm and structure for analyzing the parameters of statistically-temporal surfaces based on spatio-temporal processing of optical speckle interference signals and images using modern methods of optimal synthesis of radio engineering and coherent optoelectronic systems. In this work, an algorithm for processing optical signals scattered by statistically uneven surfaces is synthesized and investigated for problems of optimal estimation of parameters and statistical characteristics of statistically uneven surfaces. A block diagram of the optical contactless device for evaluating the parameters of statistically uneven surfaces is proposed. The limiting errors of estimation parameters of statistically uneven surfaces and the optimal installation angles of the emitters and the optical receiver are investigated. Equations are obtained for estimating the root-mean-square height of the ridges and the correlation radius of small-scale statistically uneven surfaces in the approximation of small perturbations. The proposed method for evaluating the parameters of statistically uneven surfaces allows to increase the accuracy of measurements, to conduct a non-contact assessment of the parameters - even statistically uneven surfaces that have geometric surface irregularities or located in hard-to-reach places, for example, grooves, holes, as well as products of cylindrical, spherical and other shapes.

Three-dimensional measurement method for pavement texture depth using an optimized digital speckle correlation method

Motivated by the low efficiency and poor accuracy of the existing techniques for measuring the depth of a pavement structure, we examine the characteristics of laser speckle and speckle measurement methods in relation to the depth of a pavement structure and propose a set of methods for the 3D measurement of such structures based on laser speckle and digital image processing. First, we analyze the relevant characteristics of laser speckle measurement, and then based on the relevant region and temporal sequence correlation, a faster digital speckle correlation method is used to establish a mathematical relationship between the 3D image and the structural depth. The erosion and dilation technique and mean optimization algorithm are proposed to eliminate the noise and burr of primeval 3D reconstruction. After this, a 3D point cloud of information on the depth of the pavement structure is obtained. Finally, through fitting, a good linear relationship was found between the texture depth obtained by the sand paving method and the system. From measurements using a laboratory calibration platform, it was found that the accuracy of measurement of our method can reach the subpixel level, and the running speed is high, meaning that it can be used for highly efficient and accurate detection of the depth of a road structure.

PENGARUH VARIASI SUDUT DATANG DAN SUDUT TANGKAP CAHAYA PADA NILAI KONTRAS CITRA SPEKEL BERAS BERBASIS GUI MATLAB

Rice is the staple food of Indonesian. Rice quality is a factor that needs attention because it is related to consumer health.Checking the quality of rice using digital images can be applied because it is non-invasive, so the rice will be more hygienic. The method of utilizing digital images that can be used for checking the quality of rice is LSCI (Laser Speckel Imaging). This method uses a speckle image, that contrast value is analyzedusingImageJ or MATLAB software. To obtain the optimum speckle image contrast value, the arrival angle (laser angle) and capture angle (camera angle) must be adjusted properly. Obtained angle values that produce the optimum speckle image contrast, are at the arrival angle 40 o and capture angle 30 o at 60 o data capture position. The average of the optimum contrast value is 1.2617 a.u. To simplify the speckle image processing, a speckle image contrast analysis application based on the GUI MATLAB was created. Obtained the measurement accuracy from the application is ranged from 99,99 % to 100.00%.

Investigation of the stress–strain state of racks of light steel thin-walled structures by the method of digital image correlation

The article discusses the features of the work of thin-walled profiles of light steel thin-walled structures (LSTS), used for the construction of prefabricated buildings. A brief description is given of the theory of stability of thin-walled rods based on the law of flat sections (Euler bending forms), the necessity of taking into account the seventh degree of freedom (deplanation of the cross section) when calculating LSTS for stability is revealed. The results of experimental studies of the stress–strain state (SSS) of LSTS under the influence of static compressive loads are presented. Relative deformations were monitored using strain gages and the digital image correlation method implemented in the Vic-3D digital optical system. The dependences of the main compressive stresses of the rack shelves on the applied compressive load and the field distribution of the relative longitudinal deformations of the rack walls as a result of speckle image processing in the Vic-3D system are presented. It was established that the loss of the bearing capacity of the studied LSTS from the loss of stability occurred from actual deformations, the values of which are significantly larger than the values ​​of the calculated deformations obtained from the calculation of stability based on the application of the law of flat sections.

Blood Flow Visualization by Means of Laser Speckle-Contrast Measurements under the Conditions of Nonergodicity

The influence of stationary structural inclusions in inhomogeneous strongly scattering media such as biotissues on the results of speckle-contrast measurements using temporal and spatial methods of image processing by means of laser speckle-contrast imaging is investigated. The limits of applicability of the method of laser speckle-contrast imaging are established in detail for the case in which ergodicity conditions are not fulfilled. Based on model experiments, it is demonstrated that an increase in the number of stationary scatterers relative to that of the dynamic ones in the sampling volume introduces substantial error into the results of spatial and temporal processing of speckle images for given exposure time of the detector. At the same time, analysis of spatial and temporal speckle contrasts, the values of the coefficient of speckle dynamics, along with the results of Monte-Carlo simulation of the sampling volume, revealed that the presence of a relatively thin, up to 30% of entire volume, static layer does not introduce considerable changes into the results of measurements by the method of laser speckle-contrast imaging. The exposure time of the camera, along with the number of frames used for image processing, can be varied and chosen individually for each experiment. The developed algorithms of spatial and temporal processing of images obtained by the method of laser speckle-contrast imaging were tested in the experiments on transcranial visualization of the cerebral blood flow of a mouse.

Corneal thickness measurement by secondary speckle tracking and image processing using machine-learning algorithms.

.Corneal thickness (CoT) is an important tool in the evaluation process for several disorders and in the assessment of intraocular pressure. We present a method enabling high-precision measurement of CoT based on secondary speckle tracking and processing of the information by machine-learning (ML) algorithms. The proposed configuration includes capturing by fast camera the laser beam speckle patterns backscattered from the corneal–scleral border, followed by ML processing of the image. The technique was tested on a series of phantoms having different thicknesses as well as in clinical trials on human eyes. The results show high accuracy in determination of eye CoT, and implementation is speedy in comparison with other known measurement methods.

Interference Information Processing Technology for Defects of Aluminum Honeycomb Structure in Aircraft

In order to get the interference information extraction aircraft aluminum honeycomb structure defect extraction, reliability of testing. This paper uses image processing technology to find a method about image processing composite, with the help of laser shearography detection method detecting detection. The flaw speckle results show that, after Fourier filtering, unpacking of step by step, linear trend processing of the image, gray scale processing method can extract powder composite suited interference information, effectively improve the reliability of detection of the scattered laser displacement suited, provides a new image processing program to help speckle image processing.

Fractal box-counting technique for shelf life study of grapes by laser speckle image processing

Background: In agriculture, it is essential to follow the ripening of fruits and vegetables which is a subject of interest economically. The use of optical non-destructive method is the most suitable technique for evaluating the ripening stage of fruits when they ripen off-tree and eventually to predict the optimum storage life. Many methods are recently developed in optical image processing. The texture correlation function and the fractal box counting (FBC) of biospeckle pattern have been described. Materials and Methods: The dynamic speckle patterns known as boiling speckle are produced by a coherent light illumination incident on the active material of biological tissue. A high coherent laser source He-Ne with 632 nm with neutral density filter and charge-coupled device camera are the major components of the experimental setup. The same experiment may be done by a green laser of wavelength 541 nm (green color). The same procedure continues to take the speckle images in periodically. Results and Discussion: With the help of FBC method in image processing technique, we can assess optically rough surface fruits such as grapes in this work. According to the FBC theory, the speckle images (R1) give a binary counting value D = 1.7640 at the initial stage. Gray image converted into binary image which gives the fractal counting value D = 1.7554 at later on phase. It means that the specimen (grapes) becomes dry periodically and its value is affected by the surrounding environmental condition. Conclusion: Using the dynamic speckle phenomenon or biospeckle method, we demonstrated the assessment of shelf life activity of grapes. The visual phase of the autocorrelation function gives reliable results showing the variation in activity because of the internal changes caused by decreasing water content and then becomes dry grape stage. The correlation function of speckle patternand the Fractal Box Counting (FBC) technique has been proposed as a tool to estimate the postharvest stage of grapes. The bioactivities of fruits and vegetable materials are based on Brownian motion, due to subcellular organs. This indicates the senescence or biological aging characteristics. The quantification of the biospeckle phenomena is associated with the moment of inertia, time history of speckle pattern and grey level co-occurrence matrix. We proposed a new FBC technique to assess the shelf life of grapes.

Towards real-time speckle image processing for mealiness assessment in apple fruit

ABSTRACTBiospeckle activity (during 1–25 s) of ‘Red Delicious’ apples was recorded under 680 and 780 nm laser diodes. The time history speckle pattern (THSP) images were configured and evaluated using the common biospeckle and texture descriptors. Several artificial neural networks (ANN) models were developed to predict the stiffness and juiciness of apple fruits. At the recording time of 1 s and 680 nm laser diode, the ANN models developed by texture features showed better performance in prediction of stiffness (r = 0.70 and SEP = 8.4 kN) and juiciness (r = 0.68 and SEP = 2.3 cm2) as compared to the common biospeckle features-based ones (r = 0.25 and SEP = 11.3 kN m−1 for stiffness and r = 0.29 and SEP = 3.1 cm2for juiciness). Furthermore, classification of apples into fresh, semi-mealy, and mealy groups was carried out. At the recording time of 25 s and 680 nm laser, the ANN models developed by texture features classified fresh, semi-mealy, and mealy apples with accuracies of 86.3, 65.9, and 95.5%, respectively. Reduction of the recording time to 1 s resulted in the classification accuracies of 88.2, 68.5, and 85.5% for mealy, semi-mealy, and mealy apples compared to the common biospeckle features-based ANN models with the accuracies of 82.8, 50.7, and 46.8%, respectively. These results indicated that the texture descriptors had better performance at shorter recording times in comparison with the biospeckle features which are commonly used in evaluation of biospeckle images, even though more improvements are still required.

Laser Speckle Interferometer for Deformation Measurement based on Fast Fourier Transform method

<em>In this paper, Laser speckle image processing based on Fast Fourier Transform method for displacement measurement is presented. Capturing Laser speckle images before displacement and after displacement of the specimen is the technique involved in this measurement. The cross correlation is computed by two 2Dimensional Fast Fourier Transforms (one direct and the other is inverse) and a complex multiplication. This is a non-contact, flexible measurement with high accuracy and simple operation. The results are verified by conventional gauge methods.</em>

Synchronized renal blood flow dynamics mapped with wavelet analysis of laser speckle flowmetry data.

Full-field laser speckle microscopy provides real-time imaging of superficial blood flow rate. Here we apply continuous wavelet transform to time series of speckle-estimated blood flow from each pixel of the images to map synchronous patterns in instantaneous frequency and phase on the surface of rat kidneys. The regulatory mechanism in the renal microcirculation generates oscillations in arterial blood flow at several characteristic frequencies. Our approach to laser speckle image processing allows detection of frequency and phase entrainments, visualization of their patterns, and estimation of the extent of synchronization in renal cortex dynamics.

Real-time speckle image processing

The laser dynamic speckle is an optical phenomenon produced when a laser light is reflected from an illuminated surface undergoing some kind of activity. It allows a non-destructive process for the detection of activities that are not easily observable, such as seed viability, paint drying, bacterial activities, corrosion processes, food decomposition, fruit bruising, etc. The analysis of these processes in real time makes it possible to develop important practical applications of commercial, biological and technological interest. This paper presents a new digital system based on granular computing algorithms to characterize speckle dynamics within the time domain. The selected platform to evaluate the system is Field Programmable Gate Array (FPGA) technology. The obtained minimum clock periods and latencies enable speckle image processing with real-time constraints with a maximum throughput of about thousand 512 × 512 fps.

Speckle imaging through turbulent atmosphere based on adaptable pupil segmentation

We report on the first results to our knowledge obtained with adaptable multiaperture imaging through turbulence on a horizontal atmospheric path. We show that the resolution can be improved by adaptively matching the size of the subaperture to the characteristic size of the turbulence. Further improvement is achieved by the deconvolution of a number of subimages registered simultaneously through multiple subapertures. Different implementations of multiaperture geometry, including pupil multiplication, pupil image sampling, and a plenoptic telescope, are considered. Resolution improvement has been demonstrated on a ∼550 m horizontal turbulent path, using a combination of aperture sampling, speckle image processing, and, optionally, frame selection.

Real-time blood flow visualization using the graphics processing unit

Laser speckle imaging (LSI) is a technique in which coherent light incident on a surface produces a reflected speckle pattern that is related to the underlying movement of optical scatterers, such as red blood cells, indicating blood flow. Image-processing algorithms can be applied to produce speckle flow index (SFI) maps of relative blood flow. We present a novel algorithm that employs the NVIDIA Compute Unified Device Architecture (CUDA) platform to perform laser speckle image processing on the graphics processing unit. Software written in C was integrated with CUDA and integrated into a LabVIEW Virtual Instrument (VI) that is interfaced with a monochrome CCD camera able to acquire high-resolution raw speckle images at nearly 10 fps. With the CUDA code integrated into the LabVIEW VI, the processing and display of SFI images were performed also at ∼10 fps. We present three video examples depicting real-time flow imaging during a reactive hyperemia maneuver, with fluid flow through an in vitro phantom, and a demonstration of real-time LSI during laser surgery of a port wine stain birthmark.

Statistical analysis of speckle fields in digital laser monitoring of the microstructure of paper

It has been shown that digital dynamic speckle photography is an effective method for quantitative diagnostics of changes in the structure of paper processed by pulsed discharge. A theory of the dynamic statistics of speckle fields and mathematical relations are given. In using optical magnification \(\mathfrak{M}\) = 1, the software developed permits fast statistical processing of up to 250,000 microzones in a two-dimensional CCD image of size 20 × 30 mm. The results obtained point to a high spatial and temporal resolution of the method and the possibility of its real-time realization. It has been shown that noise filtering is an important part of speckle image processing. The software permits filtering both in direct calculation of the correlation function and in the Fourier plane with the use of the fast Fourier transform.

New Insights into Image Processing of Cortical Blood Flow Monitors Using Laser Speckle Imaging

Laser speckle imaging has increasingly become a viable technique for real-time medical imaging. However, the computational intricacies and the viewing experience involved limit its usefulness for real-time monitors such as those intended for neurosurgical applications. In this paper, we propose a new technique, tLASCA, which processes statistics primarily in the temporal direction using the laser speckle contrast analysis (LASCA) equation, proposed by Briers and Webster. This technique is thoroughly compared with the existing techniques for signal processing of laser speckle images, including, the spatial-based sLASCA and the temporal-based modified laser speckle imaging (mLSI) techniques. sLASCA is an improvement of the basic LASCA technique. In sLASCA, the derived contrasts are further averaged over a predetermined number of raw speckle images. mLSI, on the other hand, is the technique in which temporal statistics are processed using the equation described by Ohtsubo and Asakura. tLASCA preserves the original image resolution similar to mLSI. tLASCA outperforms sLASCA (window size M = 5) with faster convergence of K values (5.32 versus 20.56 s), shorter per-frame processing time (0.34 versus 2.51 s), and better subjective and objective quality evaluations of contrast images. tLASCA also outperforms mLSI with faster convergence of K values (5.32 s) compared to N values (10.44 s), shorter per-frame processing time (0.34 versus 0.91 s), smaller intensity fluctuations among frames (8%-10% versus 15%-35%), and better subjective and objective quality evaluations of contrast images. As laser speckle imaging becomes an important tool for real-time monitoring of blood flows and vascular perfusion, tLASCA is proven to be the technique of choice.

Speckle interferometry methods for displacement and strain measurements using photorefractive crystal

Photorefractive crystals offer several attractive features such as high resolution and in situ processing. As the images are erasable, these crystals are suitable for read–write applications and hence find potential use in speckle photography, image processing and holography. The barium titanate (BaTiO 3) crystal as recording medium has been extensively used as a novelty filter for real-time in-plane displacement measurements employing two-beam coupling configuration. This paper presents new optical configurations in speckle shear photography to measure in-plan displacement and the strain in real time using BaTiO 3 crystal as recording medium. Speckle photography studies are made using a simple two-beam coupling configuration. In speckle shear photography, a diffused object illuminated with two parallel narrow laser beams is imaged inside the crystal, and a pump beam is added at this plane. The speckle patterns due to each beam and the pump beam produce index gratings. When the object is deformed, the speckle patterns shift consequently. We now have four speckle fields: two generated from the interaction of pump beam with the index gratings and two pertaining to deformed states directly transmitted through the crystal. Thus, the fields from respective points on the object interfere after passage through the crystal and produce the Young's fringe patterns. Due to strain, the fringes in each pattern are of different width and orientation, resulting in the generation of a Moiré pattern. The strain is obtained from the width and orientation of the fringes in the Moiré pattern. The experiments are conducted on a specimen with a notch, which is subjected to tensile loading. The in-plane displacement is measured separately in another experiment. The above studies are carried out at Nd–Yag laser.